Proteins

Proteins are made up of three core groups:

- Carboxyl Group

- Amino Acid Group

- R Group

Proteins are the most diverse molecules in the cell! They have various important roles:

• Structural: (Framework / support) - Hairs, tendons, ligaments

• Defensive: (Infection fighters) - Antibodies

• Signals: (Messengers) - Hormones

• Carrier: (Transport materials)- Hemoglobin

• Enzyme: (Catalysts)- Amylase

• Motile: (Movement) - Acetoin + Myosin

Structural Levels

Primary: Simplest level of protein structure. Sequence of amino acids polypeptide chains.

Secondary: The most common types of secondary structures are beta-pleated sheets and alpha helixes. These are the folded structures that form due to interactions between atoms. Both helix and pleated structures are held in their shape by hydrogen bonds which form between carbonyl and hydrogen amino acids.

Tertiary: Overall three-dimensional shape of a protein due to range of bonding interactions among the amino acid R groups. It is in the tertiary structure that the intermolecular reactions of the R groups will determine the three dimensional shape of the polypeptide chain. These reactions include multiple different bonds, including ionic bonds, hydrophobic bonds, hydrogen bonds, and disulfide bridges. This structure is crucial to the functions of the proteins, especially enzymes, because it is a strong bond. However, extreme conditions can cause the protein to unfold, which will cause denaturation, a loss of both structure and function of the protein.

Quaternary: Not all amino acids have this fourth structure. Hemoglobin, however, is one that does. Proteins such as these form subunits (multiple polypeptide chains). When these subunits com together, the quaternary structure is created. The same types of bonds that hold together the tertiary structure can shape the quaternary. This includes London forces and hydrogen bonds.